(a) Field of the Invention
This invention relates to improvements in a radial tire manufacturing apparatus. Also the present invention relates to improvements in a green case transfer in the radial tire manufacturing apparatus and gripping means for gripping the green case.
(b) Description of the Prior Art
I. A radial tire manufacturing apparatus
In order to assemble a high quality raw tire in the manufacture of radial tires, the following steps are required:
1. To assemble the raw tire with high precision as to the position of, relationship between and the peripheral lengths of a carcass ply, an inner liner and other members forming a carcass band, PA1 2. To set and securely enclose bead cores at a high precision in the above mentioned carcass band, PA1 3. To assemble side wall forming members of a tire precisely and securely, and PA1 4. To combine a belt-tread structure precisely and securely with an assembled green case.
At the same time, manufacturing equipment which is high in economy and productivity is required.
Under such circumstances, some methods have already been suggested and adopted but have not satisfied all of the above requirements.
Well known typical methods include a two-stage forming method, a one-stage forming method and such a forming method is as shown in Japanese Patent Publication No. 24463/1978.
The problems of the above mentioned respective forming methods shall be described in the following:
1. Two-stage forming method.
In this method, two methods of assembling a carcass band are actually adopted.
(a) One of them is a method wherein an inner liner, carcass ply and other members forming a carcass band are wound directly on a green case forming drum so as to be assembled. In this case, there are disadvantages that, as the green case is assembled on a forming drum, the time required to produce a green case per set will become so long that, as a result, the working rate of the equipment will be reduced and, on the other hand, a precise assembly and positive bonding will be difficult over the entire range in the width direction of a carcass band. Further, there have been disadvantages that, as it is necessary to concentrate many materials in one place, the material feeding apparatus will become so complicated and large that the materials will be hard to feed.
(b) In order to solve such disadvantages, there is adopted another method wherein a carcass band is assembled in advance in an independent forming step and and is then inserted into a green case forming drum. According to this method, though the productivity will improve and will be higher than 1(a) above, there is a disadvantage that, as the assembled carcass band is removed, conveyed and inserted manually and a storing place is required in the course of the conveyance, the quality of the completed tire will suffer due to the limited day control the carcass band to hold the quality uniform and due to a deformation which occurs during storage. Further, in this case, when the above mentioned carcass band assembled is inserted in advance into the green case forming drum, the center position will be displaced. This poses an obstacle to high level quality.
(c) Whichever of the above mentioned carcass band forming methods may be adopted, the convention two-stage forming method has the following further disadvantage in the case of transfering the green case formed in the first stage to the second stage, the green case will have to be taken out of the carcass forming drum of the first stage and inserted into the forming drum of the second stage. The green case is manually taken out, conveyed and inserted. This results in an obstacle to high level productivity.
(d) Further, as there is a difference (which will be conspicuous in the case of a method wherein a carcass band is assembled on a green case forming drum) between the producing capacity of the second stage and that of the first stage. Because of this, a green case storing place will be required between the first stage and second stage. This causes a reduction in quality for the completed tire due to the limited day control and deformation during storage time.
2. One-stage forming method.
In the case of this method, at a time when radial tubeless tires, particularly for trucks and buses, were in high demand in the market, and began to be produced, the one-stage forming method was noted due to the peculiarity in the structure of the tubeless tire and was partly practiced. However, this method is inferior to the above mentioned two-stage forming method in respect to efficiently producing tubeless tires and obtaining a high level quality with an increase in production ratio of tubeless tires due to the following points:
(a) The one-stage forming method is inferior to the two-stage forming method in strongly assembling a carcass ply, inner liner and other members forming a carcass band at high precision with respect to positional relationships and peripheral lengths in the band.
(b) It is inferior to the two-stage forming method in precisely and strongly assembling tire side wall forming members.
(c) It is inferior to the two-stage forming method since the number of fibers in a carcass ply enclosing the beads will be reduced.
(d) While the one-stage method is free from the trouble of the above described limited day control, the quality reduction caused by deformation at the time of intermediate storage and the trouble in handling the green case in the two-stage forming method, the one-stage method is very low in productivity.
The one-stage forming method thus has such problems as listed above and cannot exceed the above mentioned two-stage forming method.
3. Forming method shown in Japanese Patent Publication No. 24463/1978.
The forming method which is shown in the above mentioned patent is suggested as a solution to the disadvantages of the above mentioned one-stage forming method and two-stage forming method, but has such problems as set forth in the following:
(a) In this patent, as a carcass band and green case are formed in the same place, there are the same problems as in 1(a) in the above mentioned two-stage forming method.
(b) In this patent, since a carcass ply and inner liner forming a green case are not wound and assembled on a rigid drum, a strictly precise green case cannot be provided.
(c) In this patent, two green case forming drums are used alternately to increase the productivity of the green case but, when the tire size to be produced is to be changed, it will be necessary to simultaneously replace the two drums. The equipment will thus be costly and also the time required for the replacement will be longer. Under the circumstances where productivity is measured in fractions of seconds, the replacement of one more drum will bring about the disadvantage of reduced productivity.
(d) In this patent, as a green case transfer and belt-tread structure transfer are mechanically connected with each other, the green case inserting time must be long enough so as not to obstruct the belt forming operation. Also, a carcass band completed on the carcass band forming drum will be subjected to a time restriction that the green case must be delivered to the above mentioned transfer before the carcass band is returned to a material winding position. As a result, there is the problem that the operator must exactly follow the automatically operated mechanical action.
Several years ago, the number of parts forming a tire was so high and the degree of automation in the apparatus for feeding these parts or materials was so low, that the times required for the respective steps of a carcass band forming step, green case forming step and felt-tread structure forming step were different, the equipment capacities of the respective steps were unbalanced and, therefore, tires were produced in respective independent separate equipment to elevate the equipment working rates of the respective steps. This fact had its own significance as to productivity, although there were problems due to the intermediate handling requirements and some reduction in quality.
Recently, and simultaneously with progress in the simplification of the number of parts that form a tire, the automation of the material feeding apparatus has progressed so quickly and the times required for the above mentioned respective three steps have come to be so close to one another, that the significance of making the respective steps independent and separate has become low. On the other hand, the trouble of handling and the quality reduction accompanying such handling have become considerable problems. Therefor, it is required to organically handle the intermediate products between the respective steps so as to manufacture radial tires that are high in quality and are made with high productivity. That is to say:
(1) A carcass band is assembled on an expansible substantially cylindrical rigid drum (carcass band forming drum), the band is mechanically gripped and transferred with a band transfer having an expansible outside gripping mechanism and the band is automatically inserted into an expansible cylindrical rigid drum (green case forming drum). Bead cores are set on the cylindrical rigid drum and are enclosed at the ends of the carcass band. The required side wall members are then combined to complete a green case and this green case is mechanically and automatically gripped and transferred and is mechanically and automatically set on expansible drum means for making the green case toroidal. A belt-tread structure is assembled on an expansible substantially cylindrical rigid drum (belt-tread forming drum) in parallel with the above operations and is mechanically and automatically transferred to the toroidal green case on the above mentioned drum for making the green case toroidal with a belt-tread transfer having an expansible outside gripping mechanism and is combined with it to assemble a raw tire and this raw tire is mechanically and automatically taken out with the above mentioned belt-tread transfer and is further taken out of the apparatus with tire discharging means to continuously produce radial tires.
(2) The above mentioned band transfer is made to wait in the course of transferring the band, in the course of the return and in a position not obstructing the carcass band forming operation and green case forming operation so that the deviation of the above mentioned respective independent operations from the expected time can be adjusted. The above mentioned green case transfer is made to wait in the course of transferring the green case, in the course of the return and in a position not obstructing the green case forming operation and belt-tread combining operation so that the deviation of the above mentioned respective independent operations from the expected time can be adjusted. The above mentioned belt-tread transfer is made to wait in the course of transferring the belt-tread structure, in the course of the return and in a position not obstructing the belt-tread structure forming combining operation, belt-tread operation and green case inserting operation by the green case transfer so that the deviation of the above mentioned respective independent operations from the expected time can be adjusted. In this way there is greater freedom of the operations carried out by the band forming drum, belt-tread assembling drum and belt-tread and green case combining drum from a delay beyond the expected time. Even if the respective operations are not carried out exactly at the expected time, the productivity of the entire system will not be reduced.
(3) The green case transferred from the first stage to the second stage is transferred and made to wait in the space above the first stage equipment and second stage equipment so as to effectively utilize the equipment space.
Thereby, economical equipment which is high in productivity and can manufacture tires high in quality is hoped for due to these developments.
II. A green case transfer in a radial tire manufacturing apparatus:
As mentioned above, the two-stage forming method is extensively adopted as a manufacturing method of assembling and forming a green tire of a radial tire. This is a method wherein a cylindrical green case is assembled in a first stage forming means and is transformed from the cylindrical form to a toroidal form and a belt and tread are pasted on its outer periphery to complete a green tire.
In this method, in the case of transferring the above mentioned cylindrical green case from the first stage forming means to the second stage forming means, conventionally, the following manual operations are made:
(1) Removing the assembled green case from the first stage forming means,
(2) Mounting the removed green case on a conveying carriage,
(3) Conveying the green case with the carriage to a green case storage between the first stage forming means and second stage forming means,
(4) Mounting the required green case on the conveying carriage and conveying it from the storage to the second stage forming means, and
(5) Setting the green case in the second stage forming means.
Thus, there have been defects that not only a large labor force is required but also the limited day control of the green case in storage is required and troublesome, a wide storing place is required, the green case will be stained or deformed in the course of the transfer and the production of a tire which is high in quality cannot be hoped for.